SWBAT use reasoning to solve subtraction problems involving separation.

They love GAME! Separating parts from a whole is one interpretation of subtraction. Students will play a game of separating parts from a whole Minute To Win It style.

5 minutes

I want to review the part-part-whole concept for subtraction problems with my students. I will begin with 6 unifix cubes snapped together in my hand and have my students count with me to confirm the quantity and write 6 on the chalkboard. Next, I will snap 2 off the tower, write minus 2 on the board and ask them how many are left. Answer: 4. I will ask the following;

*The whole is the total amount; What was the whole for this problem?* Answer: 6

*What part went away?* Answer: 2

*What part was the difference?* Answer: 4

Now I will write the problem 8-7=1 on the board and ask them to help me label the parts.

*The whole is 8; the parts are 7 and 1.*

15 minutes

*Need: Print off the Minute to Win It game sheets and copy them front to back with the whole class practice on one side and the partners game sheet on the other. Make copies of the spinner on colored paper. Gather however many bowls you will need for each set of partners to have one. Now fill the bowls with ten unifix cubes or any object you want them to use to play the game. Check the resource section for a picture of my supplies ready to go.

I want my students to practice more problems of separation. I saw this great idea to play a game of Minute It To Win It where kids have a partner and take turns and are timed to see how many problems they can complete within a minute. I transitioned it into a subtraction game to get my kids excited to play. Also, I like the idea of one partner having a certain quantity and the other partner getting to take away so many.

Your students will be divided into partners, so you only need enough spinners for half of your class. You can laminate your spinners to make them stronger and for future use. I will be using the same spinners to build our whole class problems. This will provide them the opportunity to begin seeing the structure of the problems we are creating. Also, I will have a Styrofoam bowl as a container for my cubes to lay in until I grab them. When I finish each problem that will be my place to put them and be ready for the next problem.

I will have my students gather at our carpet and I will pick someone to be my partner. I will spin the first spinner and grab that many cubes and show my class. Then my partner will spin the second spinner and take that many cubes and place them back in the bowl. Look at the resources of my partner taking his turn. This will leave only the difference out for them to see and will support my students struggling with number sense to ensure no confusion with cubes laying everywhere. As my partner and I solve these problems I will continue to ask my class what do we do next, so I can check for understanding of the directions. Students will be recording answers on their worksheet of our whole class problems.

We will continue together until all problems are solved then I will begin getting them ready for their independent practice.

10 minutes

The Common core standards expect first graders to solve subtraction problems by taking away and using objects. This will be a great activity for my students struggling with number sense because they will actually have manipulatives in their hands and have some taken away. This will provide them with more opportunities to build their fluency in subtraction for standard 1.OA.C.6 and to use a math tool (cubes) to build models for mathematics. Using the cubes as tools to build a model for their equations will help them become more proficient in solving their subtraction problems and help them explore the underlying ideas in MP5.

The game sheets and spinners are in the resource section. You should have them from our whole group activity. Have them turn their paper over to the partner side. Allow them to pick their own partner or you pick for them.

Student A spins the first spinner and grabs that many cubes, then records their answer in the first column.

Student B spins the second spinner and takes that many cubes from Student A, places them back in the bowl and records that number in the second column. The students check to see how many are left and records the answer. All the cubes go back in the bowl and the second turn begins.

I will not time them on the first problem, so they get time to understand the process of the game. Starting with round 2, I will tell them they have a minute to complete their problem. I will ask them to put their hands on their head when they are done. Look at the resource section to see the game in action and a picture of a completed partner sheet.

10 minutes

To help them synthesize what we explored today and connect their learning word problems, I have students write a story problem about the game we played. I quickly model how to match one of their number sentences to a story problem about the game on the board: “I rolled a 6 and got out 6 cubes. My partner rolled a 4, so we took away 4 cubes. We ended up with 2 cubes.”

I then erase the numbers and leave the sentence stems. I send students off to write their own versions with number sentences they explored. Those who finish early can illustrate the problem and/or share their story with a partner.